1. Field of the Invention
The present invention relates to a color separation apparatus, a color separation method, and a color separation program, and more particularly to a color separation apparatus, a color separation method, and a color separation program, for applying color separation to image data for printing to make colors to be used in a printer.
2. Description of the Related Art
When image data is printed, color separation is applied to the image data to make a dot image for each of color materials (process colors (CMYK), for example), and overprinting is performed by using a printing plate on which dots corresponding to each of the color materials are formed so that gradation of the image data is expressed. In a case where dot images corresponding to a plurality of color materials are overprinted, a pattern with an image formation such as a moire and a rosette pattern sometimes occurs depending on a position and an angle of a dot, screen ruling, and a shape.
Japanese Patent Application Laid-Open No. 2007-116287 (patent literature 1) discloses a method of evaluating noise information having strong periodicity in dot images when color separation is applied to image data. In Japanese Patent Application Laid-Open No. 2007-116287, a printed patch image is read, and each pixel data of the image data is resolved into RGB data to be transferred to an optimization unit 12 by being converted into color information (L*, a*, and b*, for example) in a uniform color space. The optimization unit 12 calculates a graininess evaluation value on the basis of L* based on parameter of granularity and ink concentration determined by a UI unit 11 (refer to the paragraphs [0019] to [0023]).